Method of polarographic analysis of lactic acid and lactate

Abstract

A method of measuring lactic acid or lactate and derivatives thereof in liquids which is extremely versatile and is suitable for use in a number of areas such as the rapid measurement of lactic acid in whole blood, the ratio of lactic acid to pyruvic acid in whole blood, in-vivo measurement of lactic acid and the study of living lactic acid-producing cells. The acid or lactate is measured by reacting the lactic acid with lactic oxidase to produce pyruvate and H 2 O 2 . The H 2 O 2 is then measured polarographically. The current produced is directly proportional to the lactate level. Preferably, the lactic oxidase is trapped between two semi-permeable membranes. One membrane is placed in contact with an electrolyte at the tip of an electrode and the second membrane contacts the liquid being tested.

Having thus described my invention, I claim: 
     
       1. The method of measuring lactic acid or derivatives thereof in a liquid and subsequently measuring pyruvate in said liquid comprising reacting said lactic acid or said derivatives thereof with lactic oxidase to produce pyruvate and hydrogen peroxide and measuring said hydrogen peroxide polarographically; and contacting said pyruvate with pyruvate oxidase, thereby producing acetic acid and hydrogen peroxide and measuring the produced hydrogen peroxide polarographically.   
     
     
       2. A method of measuring the ratio of lactic acid or derivatives thereof to pyruvic acid or derivatives thereof in a liquid comprising measuring the lactic acid in said liquid by reacting said lactic acid or derivative thereof with lactic oxidase, thereby producing hydrogen peroxide and pyruvate and measuring said hydrogen peroxide polarographically, and further comprising converting pyruvic acid in said liquid to lactic acid and subsequently measuring the lactic acid in said blood. 
     
     
       3. The method claimed in claim 2 wherein said liquid is whole mammalian blood. 
     
     
       4. The method claimed in claim 2 wherein said lactic oxidase is trapped between an inner and an outer membrane layer wherein said outer membrane layer separates said liquid from said enzyme and allows lactic acid or derivatives thereof to pass therethrough, and said inner membrane separates said enzyme from an electrolyte and allows hydrogen peroxide to pass therethrough. 
     
     
       5. The method claimed in claim 4 wherein said anode is separated from said inner membrane by a capillary layer of electrolyte. 
     
     
       6. The method claimed in claim 2 wherein said pyruvic acid in said liquid is converted to lactic acid by adding NADH and lactic dehydrogenase to said liquid. 
     
     
       7. A method of measuring the ratio of lactic acid or derivatives thereof to pyruvic acid or derivatives thereof in whole mammalian blood comprising measuring the lactic acid in said blood by reacting said lactic acid or derivatives thereof with lactic oxidase to produce pyruvate and hydrogen peroxide and measuring the hydrogen peroxide polarographically; and adding NADH and lactic dehydrogenase to said blood, thereby converting pyruvic acid or derivatives thereof in said blood to lactic acid and subsequently reacting the lactic acid with lactic oxidase to produce hydrogen peroxide and measuring the hydrogen peroxide polarographically.